Thin film composite hollow fiber membranes fabrication systems

ABSTRACT

Apparatuses and methods for fabricating thin film composite hollow fiber membranes. In some implementations, an apparatus is used to remove excess first solution from a hollow fiber that has been immersed in a first solution. In some implementations, the method and apparatuses include flowing a gas, for example, compressed gas or ambient air, past a surface of a hollow fiber that has been immersed in a first solution prior to immersion in a second solution. In some implementations, the gas is flowed past the surface under positive pressure, while in other implementations the gas is flowed under negative pressure, for example, vacuum. The apparatuses and devices can be used to produce thin film composite hollow fiber membranes without pressing or damaging the hollow fiber.

TECHNICAL FIELD

This document relates to methods and apparatuses for the fabrication ofthin film composite hollow fiber membranes.

BACKGROUND

Thin film composite membranes are semipermeable membranes. Thesemembranes can be used in purification and separation processes such aswater purification, including nanofiltration and reverse osmosis. Thesemembranes can also be used in gas separations, for example, heliumextraction and hydrogen recovery from natural gas processing. Thin filmcomposite membranes can be planar or hollow fiber structures thatseparate two environments or phases.

SUMMARY

This disclosure describes thin film composite hollow fiber membranefabrication systems.

The following units of measure have been mentioned in this disclosure:

Unit of Measure Full form mm millimeter um micrometer nm nanometer cm²square centimeter psi pounds per square inch ° C. degrees Celsius wt %percent by weight wt/vol % percent weight by volume

In some implementations, an apparatus for fabricating thin filmcomposite hollow fiber membranes includes a housing, an inlet formed ona first surface of the housing, and an outlet formed on a second surfaceof the housing opposite the first surface. The housing defines a firsthollow passage between the inlet and the outlet. The first hollowpassage is configured to allow a hollow fiber to pass through thehousing. The apparatus includes a vacuum port formed on a third surfaceof the housing. The housing defines a second hollow passage between thefirst hollow passage and the vacuum port. The vacuum port is configuredto draw gas from the inlet and the outlet, and through the first hollowpassage and the second hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The third surface is substantiallyperpendicular to the first surface or the second surface.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second hollow passage issubstantially perpendicular to the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The housing includes a first plate and asecond plate configured to be joined together to form the housing.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate defines at least aportion of the first hollow passage and the second plate defines aremainder of the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second plate defines the secondhollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate and the second plate areseparably coupled by a coupling mechanism.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The coupling mechanism includes a hingeor a magnet or a hinge and a magnet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate has a substantiallyrectangular cross-section and the second plate has a substantiallyT-shaped cross-section.

In some implementations, a system for fabricating thin film compositehollow fiber membranes includes an apparatus including a housing, aninlet formed on a first surface of the housing, and an outlet formed ona second surface of the housing opposite the first surface. The housingdefines a first hollow passage between the inlet and the outlet, and thefirst hollow passage is configured to allow a hollow fiber to passthrough the housing. The apparatus includes a vacuum port formed on athird surface of the housing. The housing defines a second hollowpassage between the first hollow passage and the vacuum port, and thevacuum port is configured to draw gas from the inlet and the outlet andthrough the first hollow passage and the second hollow passage. A vacuumsource can be coupled to the vacuum port, and the vacuum source can beconfigured to apply vacuum to the vacuum port to draw the gas from theinlet and the outlet and through the first hollow passage and the secondhollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The housing includes a first plate and asecond plate configured to be joined together to form the housing.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate defines at least aportion of the first hollow passage and the second plate defines aremainder of the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second plate defines the secondhollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate and the second plate areseparably coupled by a coupling mechanism.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The coupling mechanism includes a hingeor a magnet or a hinge and a magnet.

In some implementations, a method of fabricating thin film compositehollow fiber membranes includes passing a hollow fiber through a firsthollow passage defined by a housing between an inlet formed on a firstsurface of the housing and an outlet formed on a second surface of thehousing opposite the first surface, wherein the hollow fiber is immersedin a first solution prior to passing the hollow fiber through the firsthollow passage. The method includes, while passing the hollow fiberthrough the first hollow passage, drawing, by vacuum, a gas through thefirst hollow passage and over the hollow fiber through a second hollowpassage defined by the housing. The second hollow passage terminates ina vacuum port formed on a third surface of the housing. Drawing the gasover the hollow fiber removes at least a portion of the first solutionfrom an outer surface of the hollow fiber.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. After passing the hollow fiber throughthe outlet, the hollow fiber is immersed in a second solution. The firstsolution and the second solution are immiscible, wherein contact betweenthe first solution and the second solution causes a polymerizationreaction at an interface of the first solution and the second solution.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. Immersing the hollow fiber in a firstsolution can include immersing the hollow fiber in an aqueous solution.The aqueous solution includes monomeric arylene polyamine.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. Immersing the hollow fiber in a secondsolution can include immersing the hollow fiber in a solution thatincludes a monomeric acyl halide.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. Drawing, by vacuum, the gas through thefirst hollow passage and over the hollow fiber through the second hollowpassage can include drawing the gas through the inlet and the outlettowards the vacuum port.

In some implementations, an apparatus for fabricating thin filmcomposite hollow fiber membranes can include a housing, an inlet formedon a first surface of the housing, and an outlet formed on a secondsurface of the housing opposite the first surface. The housing defines afirst hollow passage between the inlet and the outlet, and the firsthollow passage is configured to allow a hollow fiber to pass through thehousing in a direction from the inlet to the outlet. The apparatusincludes a compressed gas port formed on the housing. The housingdefines a second hollow passage between the first hollow passage and thecompressed gas port. The compressed gas port is configured to flowcompressed gas through the second hollow passage toward the first hollowpassage, toward the inlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The compressed gas port is formed on thesecond surface adjacent the outlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The apparatus can include a secondcompressed gas port formed on the housing. The housing defines a thirdhollow passage between the first hollow passage and the secondcompressed gas port. The second compressed gas port is configured toflow compressed gas through the third hollow passage and into the firsthollow passage towards the inlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second hollow passage and the thirdhollow passage share a common outlet to the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The common outlet is positionedsubstantially at a mid-point of the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The housing includes a first plate and asecond plate configured to be joined together to form the housing.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate defines at least aportion of the first hollow passage and the second plate defines aremainder of the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second plate defines the secondhollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate and the second plate areseparably coupled by a coupling mechanism.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The coupling mechanism includes a hingeor a magnet or a hinge and a magnet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first plate has a substantiallyrectangular cross-section and the second plate has a substantiallyT-shaped cross-section.

In some implementations, a system for fabricating thin film compositehollow fiber membranes includes an apparatus. The apparatus includes ahousing, an inlet formed on a first surface of the housing, and anoutlet formed on a second surface of the housing opposite the firstsurface. The housing defines a first hollow passage between the inletand the outlet. The first hollow passage is configured to allow a hollowfiber to pass through the housing in a direction from the inlet to theoutlet. The apparatus includes a compressed gas port formed on thehousing. The housing defines a second hollow passage between the firsthollow passage and the compressed gas port. The compressed gas port isconfigured to flow compressed gas through the second hollow passagetoward the first hollow passage, toward the inlet. The system includes acompressed gas source coupled to the compressed gas port. The compressedgas source is configured to flow compressed gas to the compressed gasport and through the second hollow passage and the first hollow passagetoward the inlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The compressed gas port is formed on thesecond surface adjacent the outlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The system includes a second compressedgas port formed on the housing. The housing defines a third hollowpassage between the first hollow passage and the second compressed gasport. The second compressed gas port is configured to flow compressedgas through the third hollow passage into the first hollow passage intowards the inlet. The compressed gas source is coupled to the secondcompressed gas port to flow compressed gas to the second compressed gasport and through the third hollow passage and the first hollow passagetoward the inlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second hollow passage and the thirdhollow passage share a common outlet to the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The common outlet is positionedsubstantially at a mid-point of the first hollow passage.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The housing includes a first plate and asecond plate configured to be joined together to form the housing.

In some implementations, a method of fabricating thin film compositehollow fiber membranes includes passing a hollow fiber through a firsthollow passage defined by a housing between an inlet formed on a firstsurface of the housing and an outlet formed on a second surface of thehousing opposite the first surface. The hollow fiber is immersed in afirst solution prior to passing the hollow fiber through the firsthollow passage from the inlet toward the outlet. A compressed gas sourceflows compressed gas through a second hollow passage defined by thehousing and through the first hollow passage while the hollow fiberpasses through the first hollow passage. The second hollow passageoriginates at a compressed gas port formed on the housing. Thecompressed gas flows toward the inlet in a direction at least partiallyopposite a direction in which the hollow fiber is passed. Flowing thecompressed gas over the hollow fiber removes at least a portion of thefirst solution from an outer surface of the hollow fiber.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. After passing the hollow fiber throughthe outlet, the hollow fiber is immersed in a second solution. The firstsolution and the second solution are immiscible, and contact between thefirst solution and the second solution causes a polymerization reactionat an interface of the first solution and the second solution.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first solution includes an aqueoussolution. The aqueous solution includes a monomeric arylene polyamine,and the second solution includes a monomeric acyl halide.

In some implementations, an apparatus for fabricating thin filmcomposite hollow fiber membranes includes a first tubular member fluidlycoupled to a compressed gas inlet port, and a second tubular memberpositioned coaxially within the first tubular member. The second tubularmember includes a circumferential wall having a plurality of apertures.The second tubular member is configured to receive a hollow fiberthrough a hollow portion of the second tubular member. The first tubularmember is configured to flow compressed gas received through thecompressed gas inlet port into the hollow portion through the pluralityof apertures.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. Each aperture is a through-hole formedin the circumferential wall of the second tubular member. Each aperturehas an axis, and an angle between the axis of each aperture and the axisof the second tubular member is configured to flow the compressed gasover the hollow fiber in a direction at least partially opposite to adirection in which the hollow fiber is passed through the hollow portionof the second tubular member.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angle is greater than zero degreesand less than ninety degrees.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angle is substantially 45 degrees.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angles of the apertures are equal toeach other.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angles of the apertures aredifferent from each other.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second tubular member is positionedcoaxially within the first tubular member. The second tubular memberdefines an annular region between an inner surface of the first tubularmember and an outer surface of the circumferential wall of the secondtubular member. The annular region is sealed to force the compressed gasinto the hollow portion of the second tubular member through theplurality of apertures.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The compressed gas inlet port is formedon a circumferential surface of the first tubular member atsubstantially a midway location between ends of the first tubularmember.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The apparatus includes a third tubularmember attached to the first tubular member. A first end of the thirdtubular member is fluidly coupled to a circumferential surface of thefirst tubular member. The compressed gas inlet port is formed on asecond end of the third tubular member.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The first tubular member and the thirdtubular member are substantially perpendicular to each other.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The third tubular member is attached tothe first tubular member at a location substantially midway between endsof the first tubular member.

In some implementations, a system for fabricating thin film compositehollow fiber membranes includes an apparatus. The apparatus includes afirst tubular member fluidly coupled to a compressed gas inlet port, anda second tubular member positioned coaxially within the first tubularmember. The second tubular member includes a circumferential wall havinga plurality of apertures. The second tubular member is configured toreceive a hollow fiber through a hollow portion of the second tubularmember. The first tubular member is configured to flow compressed gasreceived through the compressed gas inlet port into the hollow portionthrough the plurality of apertures. The system includes a compressed gassource coupled to the compressed gas port. The compressed gas source isconfigured to flow compressed gas to the compressed gas port and throughthe plurality of apertures into the hollow portion of the second tubularmember towards the inlet.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. Each aperture is a through-hole formedin the circumferential wall. Each aperture has an axis, and the anglebetween the axis of each aperture and the axis of the second tubularmember is configured to flow the compressed gas over the hollow fiber ina direction at least partially opposite to a direction in which thehollow fiber is passed through the hollow portion of the second tubularmember.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angle is greater than zero degreesand less than ninety degrees.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angle is substantially 45 degrees.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angles of the apertures are equal toeach other.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The angles of the apertures aredifferent from each other.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. The second tubular member is positionedcoaxially within the first tubular member. The second tubular memberdefines an annular region between an inner surface of the first tubularmember and an outer surface of the circumferential wall of the secondtubular member. The annular region is sealed to force the compressed gasinto the hollow portion of the second tubular member through theplurality of apertures.

In some implementations, a method of fabricating thin film compositehollow fiber membranes includes coaxially positioning a first tubularmember around a second tubular member to define an annular regionbetween the first tubular member and the second tubular member. Themethod includes passing a hollow fiber through a hollow portion of thesecond tubular member from a first end of the second tubular membertoward a second end of the second tubular member. The hollow fiber isimmersed in a first solution prior to passing the hollow fiber throughthe first tubular member. Compressed gas is flowed into the annularregion and into the hollow portion through a plurality of aperturesformed on a circumferential wall of the second tubular member in adirection at least partially opposite the direction in which the hollowfiber is passed through the second tubular member. Flowing thecompressed gas over the hollow fiber removes at least a portion of thefirst solution from an outer surface of the hollow fiber.

This aspect, taken alone or combinable with any other aspect, caninclude the following features. After passing the hollow fiber throughthe second tubular member, the hollow fiber is immersed in a secondsolution. The first solution and the second solution are immiscible andcontact between the first solution and the second solution causes apolymerization reaction at an interface of the first solution and thesecond solution.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings and the description that follows.Other features, objects, and advantages of the disclosure will beapparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes.

FIG. 2A shows an example of a first implementation of an apparatus.

FIG. 2B shows an example of a front view of a first implementation of anapparatus.

FIG. 2C shows an example of a cross-sectional top view of a firstimplementation of an apparatus.

FIG. 2D shows an example of a cross-sectional side view of a firstimplementation of an apparatus.

FIG. 3 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes using an apparatus.

FIG. 4 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes.

FIG. 5A shows an example of a second implementation of an apparatus.

FIG. 5B shows an example of a front view of a second implementation ofan apparatus.

FIG. 5C shows an example of a cross-sectional top view of a secondimplementation of an apparatus.

FIG. 5D shows an example of a cross-sectional side view of a secondimplementation of an apparatus.

FIG. 6 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes using a second implementation of anapparatus.

FIG. 7 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes using a second implementation of anapparatus.

FIG. 8A shows an example of a third implementation of an apparatus.

FIG. 8B shows an example of a top view of a third implementation of anapparatus.

FIG. 8C shows an example of a cross-sectional side view of a thirdimplementation of an apparatus.

FIG. 9 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes using an apparatus.

FIG. 10 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Interfacial polymerization can include reacting two or more monomersthat are dissolved separately in immiscible liquids. A membrane isformed at the interface between these two solutions. For example, amembrane can be formed at the interface between an aqueous solutioncontaining monomeric arylene polyamine and a solution containingmonomeric acyl halide. Planar polymeric nanofiltration and reverseosmosis membranes can be produced by immiscible solutions of aqueous1,3-phenylenediamine (m-PDA) and trimesoyl chloride (TMC) in n-hexane.Upon contact of the two solutions on the outer surface of a planarsupport structure, m-PDA and TMC polymerize. As the polymerizationreaction proceeds, the interfacial film becomes a barrier that slowsfurther reaction. Accordingly, interfacial polymer films are generallyultrathin, for example, less than 500 nm in thickness.

Interfacial polymerization can be used to prepare membranes byintroducing a first solution to a support surface and then exposing thesupport surface to a second solution. The first solution can be appliedto the support surface by spraying an aerosol of the first solution onthe surface, or contacting the surface in a bath of the first solution.In both of these approaches, excess first solution is removed from thesupport surface. A single excess drop can create defects in the thinfilm membrane, which reduces the performance of the membrane. Forexample, a single excess droplet of the first solution can cause theformation of free bodies on the support surface. These free bodies falleasily from the film after the polymerization reaction, and can causethe membrane performance to drop significantly.

One method of preparing thin films using interfacial polymerizationincludes the use of rollers and solution baths to form flat sheetmembranes. In this method, a flat support sheet travels along a systemof rollers. The flat surface is immersed in a first solution, forexample, aqueous m-PDA. The flat sheet is then pressed between tworollers, referred to as nip rollers, to remove excess first solution.The support surface is then immersed in a second solution, for example,TMC in n-hexane, to result in the formation of a thin film membrane onthe flat surface.

This disclosure describes devices and methods for forming thin filmcomposite hollow fiber membranes as opposed to flat sheet membranes. Thesystem described above to form flat sheet membranes is not suitable forforming thin film composite hollow fiber membranes due to differences ingeometry between the two types of membranes. For example, pressing ahollow fiber between nip rollers causes the fiber to collapse, and caninduce breakage or damage to the hollow fiber. This disclosure describesmethods and apparatuses that flow a gas (for example, compressed gas orambient air) past a surface of a hollow fiber that has been immersed ina first solution prior to immersion in a second solution. In someimplementations, the gas is flowed past the surface under positivepressure, while, in other implementations, the gas is flowed undernegative pressure, for example, vacuum. Flow parameters of the gas areselected to remove the excess first solution. Using the apparatusesdescribed in this disclosure can remove excess first solution, allow forthe use of a roller system (described below with reference to FIG. 1),and allow for the continuous movement of the hollow fibers along rollersand through the two solution reservoirs.

Reference will now be made in detail to certain embodiments of thedisclosed subject matter, examples of which are illustrated in part inthe accompanying drawings. While the disclosed subject matter will bedescribed in conjunction with the enumerated claims, it will beunderstood that the example subject matter is not intended to limit theclaims to the disclosed subject matter. Provided in this disclosure, inpart, are methods and apparatuses for producing thin film compositehollow fiber membranes.

FIG. 1 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes using an apparatus. A system 100 caninclude a hollow fiber 150 that can travel between or over a series ofrollers 101. The hollow fiber 150 can be a semi-permeable hollow fiber.The rollers 101 are positioned to immerse the hollow fiber 150 in afirst solution 102. The first solution 102 can be held in a firstreservoir 103. The hollow fiber then passes through one or moreapparatuses 200, 500, or 800. The hollow fiber can then be immersed in asecond solution 104. The second solution 104 can be held in a secondreservoir 104. As described in detail with reference to the figures thatfollow, each of the apparatuses 200, 500 or 800 can remove excess firstsolution from a surface of the hollow fiber 150 after the hollow fiber150 has been immersed in the first solution 102 and before the hollowfiber 150 is immersed in the second solution 104.

FIG. 2A shows an example of a perspective view of a first implementationof an apparatus 200. The apparatus 200 can include a housing 201. Thehousing can comprise metal or plastic, for example,polytetrafluoroethylene, polyethylene, polypropylene, or acrylic. Ahollow fiber that has been immersed in the first solution (for example,the first solution 102 of FIG. 1) is passed through the apparatus 200from an inlet to an outlet via a hollow passage within the apparatus200. As the hollow fiber passes through the apparatus 200, a gas isflowed past a surface of the hollow fiber through the hollow passageformed. The flowing gas removes excess first solution from the surfaceof the hollow fiber. Removal of the excess first solution improves thequality of the membrane that results from interfacial polymerization.For example, excess first solution on the hollow fiber causes defects inthe membrane, accordingly, removing the excess first solution improvesthe quality and subsequent performance of the membrane.

In some implementations, the housing includes two plates, a first plate212 and a second plate 214. The housing 201 is formed by positioning andaligning the top and bottom plates. The first plate 212 can be a topplate and the second plate 214 can be a bottom plate. In someimplementations, the first plate 212 can be the bottom plate and thesecond plate 214 can be the top plate. The first plate 212 can have afirst surface 203 and a second surface 205, where the second surface 205is opposite and parallel to the first surface 203 (FIG. 2A, 2D). Thesecond plate 214 can have a first surface 215 and a second surface 217,where the second surface 217 is opposite and parallel to the firstsurface 205 (FIG. 2A, 2D). In some implementations, the first plate 212and the second plate 214 are separably coupled by a coupling mechanism.This reversible coupling can be beneficial for making adjustments to thehollow fiber or for threading the hollow fiber through the apparatusinitially. The coupling mechanism can include a hinge 216, a magnet 218,multiple magnets 218, or a combination of two or all of them (FIG. 2B).Any coupling mechanism that allows the first and second plate to bereversibly opened and closed can be suitable, for example, a hinge and aclasp.

The first surface 203 of the first plate 212 can define at least aportion of the inlet 202, and the first surface 215 of the second plate212 can define a remainder of the inlet 202. The second surface 205 ofthe first plate 212 can define at least a portion of the outlet 204, andthe second surface 217 of the second plate 214 can define a remainder ofthe outlet 204 (FIG. 2D). A first hollow passage 206 connects the inletand the outlet (FIGS. 2C, 2D). The first plate 212 can define a firstportion of the first hollow passage 206 and the second plate 214 candefine a second portion of the first hollow passage 206. Accordingly, insome implementations the first hollow passage 206 is formed when thefirst and second plates are joined together (FIG. 2D).

The second plate can include a third surface 209 perpendicular to thefirst and second surfaces of the first and second plates (FIG. 2D). Thethird surface can include a vacuum port 208. The vacuum port 208 isconfigured to be connected to a vacuum source. A second hollow passage210 connects the vacuum port to the first hollow passage 206 (FIGS. 2B,2C, 2D). The second hollow passage 210 is configured for the movement ofair or gas through the second hollow passage. The hollow fiber 250 doesnot pass through the second hollow passage 210.

FIG. 2B shows an example of a front view of the apparatus 200 withplates 212 and 214. The first plate 212 can have a substantiallyrectangular cross-section. The substantially rectangular cross-sectionallows the hollow fiber to pass through the apparatus 200. The secondplate 214 can have a substantially T-shaped cross-section. Thesubstantially T-shaped cross-section allows the vacuum port 208 to beplaced at an optimal distance and an angle relative to the first hollowpassage 206. This allows for the vacuum port and vacuum source to removeexcess first solution from the hollow fiber without damaging the hollowfiber. As shown in FIG. 2B, the first plate 212 can define at least aportion of the inlet 202, and the second plate 214 can define aremainder of the inlet 202. The inlet 202, outlet 204, and first hollowpassage 206 can be sufficiently large to allow a hollow fiber to passthrough the apparatus 200 without coming into contact with the sides ofthe first hollow passage 206. The inlet, outlet, and first hollowpassage can have, for example, a diameter of 0.5 to 10 mm.Alternatively, the inlet, outlet, and first hollow passage can have, forexample, a diameter of 0.5 to 2.0 mm. Further, the inlet, outlet, andfirst hollow passage can be configured to accommodate the desired hollowfiber. For example, high pressure applications require thin filmcomposite hollow fiber membranes that are thin enough to withstandoperating pressures. A hollow microfiber with a diameter of 80 μm can beused for high-pressure applications such as gas separation, reverseosmosis, or nanofiltration. Alternatively, low pressure applicationssuch as microfiltration or ultrafiltration require thicker thin filmcomposite hollow fiber membranes in order to minimize pressure dropthrough the bore of the fiber. A hollow fiber with a diameter of 1.5 mmcan be used for ultrafiltration or microfiltration. Accordingly, theinlet, outlet, and first hollow passage can be configured to these orother hollow fiber diameters. In some implementations, the diameter ofthe inlet, outlet, and first hollow passage can be between 150%-200%wider than the diameter of the hollow fiber. The inlet 202, outlet 204,and first hollow passage 206 can have any cross-sectional shape that canaccommodate the hollow fiber. For example, the inlet, outlet, and firsthollow passage can have a triangular, rectangular, star-shaped orsubstantially circular passage.

The second plate 214 can include the vacuum port 208, as describedpreviously. The second plate 214 can define a second hollow passage 210formed between the vacuum port 208 and the first hollow passage 206. Thesecond hollow passage 210 is configured for the movement of air or gasthrough the second hollow passage. The hollow fiber 250 does not passthrough the second hollow passage 210. The second hollow passage fluidlyconnects the vacuum port 208 and the first hollow passage 206. Thesecond hollow passage can connect to the first hollow passage at a pointsubstantially in the middle of the first hollow passage 206.Accordingly, when a vacuum is applied to the vacuum port 208, gas movesfrom the inlet 202 or the outlet 202 through the first hollow passage206 towards the second hollow passage 210, and through the second hollowpassage 210 towards the vacuum source. In implementations where thesecond hollow passage 210 connects to a point substantially in themiddle of the first hollow passage 206, the gas moves from both theinlet 202 and the outlet 204 towards the second hollow passage 210. Insome implementations, the gas is ambient air. In some implementations,the gas is an inert gas, for example nitrogen. The flow rate of the airor gas towards the second hollow passage 210 can be optimized, forexample by optimizing for the diameter of the first hollow passage 206,the length of the first hollow passage 206, or the diameter of thehollow fiber.

FIG. 2C shows an example of a cross-sectional top view of the apparatus200. As shown in FIG. 2C, the hollow fiber 250 can pass through theapparatus 200 from the inlet 202 to the outlet 204 via the first hollowpassage 206. The inlet and the outlet can be formed by the first surface(203/215) and second surfaces (205/217) of the first and second plates.In some implementations, the second hollow passage 210 connects to thefirst hollow passage 206 at a point that is substantially in the middleof the first hollow passage 206.

FIG. 2D shows an example of a cross-sectional side view of the apparatus200. The apparatus 200 can include a first plate (212) and a secondplate (214) with first surfaces (203/215) and second surfaces (205/217)as described previously. The apparatus 200 can include a vacuum port 208formed on a third surface 209 of the second plate 214, with the secondplate 214 defining a second hollow passage 210 between the first hollowpassage 206 and the vacuum port 208. The second hollow passage 210 canconnect to the first hollow passage 206 at a point substantially in themiddle of the first hollow passage 206. In some implementations, thesecond hollow passage 210 can connect to the first hollow passage at apoint substantially at one end of the first hollow passage 206. In someimplementations, the third surface 209 is perpendicular to the firstsurfaces (203/215) and second surfaces (205/217). In someimplementations, the second hollow passage 210 is substantiallyperpendicular to the first hollow passage 206. In some implementations,the second hollow passage 210 is angled relative to the first hollowpassage 206. In some implementations, the angle of the second hollowpassage is greater than zero degrees and less than ninety degrees. Insome implementations, the angle is substantially 45 degrees. In someimplementations, the second plate 214 defines the vacuum port 208 andthe second hollow passage 210. The vacuum port 208 can be configured tobe connected to a vacuum source to draw gas from the inlet 202 and theoutlet 204, through the first hollow passage 206 and the second hollowpassage 210 as described previously. The gas can be, for example,ambient air or an inert gas such as nitrogen.

In some implementations, the apparatus 200 could include more than onevacuum port, for example, multiple vacuum ports in the third surface209, with additional hollow passages that connect the vacuum ports tothe first follow passage 206.

In an alternative embodiment, the inlet 202, outlet 204, first hollowpassage 206, vacuum port 208, and second hollow passage 210 can bedefined by the first plate 212. In another alternative embodiment, theinlet 202, outlet 204, first hollow passage 206, vacuum port 208 andsecond hollow passage 210 can be defined by the second plate 214. Thesecond hollow passage 210 is configured for the movement of air or gasthrough the second hollow passage. The hollow fiber 250 does not passthrough the second hollow passage 210.

FIG. 3 shows an example of a system configured to produce thin filmcomposite hollow fiber membranes using an apparatus. In someimplementations, the apparatus 200 can be part of a system 390 forproducing a thin film composite on the outer surface of a hollow fibermembrane. The system can include a hollow fiber 350 that is configuredto be passed between two bobbins 302 and 304 over a series of rollers303. The hollow fiber 350 can be a semi-permeable hollow fiber membrane.The hollow fiber can be wound around the first bobbin 302 to create aspool of hollow fiber. The hollow fiber 350 can then unspool from thefirst bobbin 302 and travel along the series of rollers 303. The rollersare positioned to direct the hollow fiber 350 into a first solution 306,in order to saturate or coat the hollow fiber 350 with the firstsolution. The first solution 306 can be held in a first reservoir 307.The first solution can be an aqueous solution containing monomericarylene polyamine, for example, an aqueous solution of1,3-phenylenediamine. The hollow fiber then passes through the apparatus200. A vacuum 310 is connected to the apparatus 200 to remove the excessfirst solution from the hollow fiber 350.

The rollers are positioned to subsequently immerse the hollow fiber 350in a second solution 308. The second solution can be held in a secondreservoir 309. The second solution can be a water immiscible solventcontaining monomeric acyl halide, for example, a solution of trimesoylchloride in n-hexane. After immersing in the second solution, the hollowfiber includes a thin film composite on the outer surface of themembrane, forming a thin film composite hollow fiber membrane 351. Thethin film composite hollow fiber membrane 351 then passes through an airdrying tower 312. The air drying tower 312 is configured to evaporateunreacted second solution and thermally cure the formed compositemembrane. The air drying tower 312 can include a heat gun or a dryer.The heat supplied by the air drying tower 312 can reach temperatures of150° C. to dry and cure the thin film composite hollow fiber membrane.The thin film composite hollow fiber membrane 351 can then travel to asecond bobbin 304 configured to receive the thin film composite hollowfiber membrane 351. The thin film composite hollow fiber membrane 351can be wound around the second bobbin 304.

The system can include a motor to drive the movement of the hollowfiber, for example, by driving the rotation of the bobbins, the rollers,or a combination of the bobbins and rollers. In some implementations,the second bobbin 304 is connected to a motor and set to a speed thatallows for removal of the excess first solution 306 as well as drying ofthe thin film composite hollow fiber membrane 351. In someimplementations, the rotation of the first bobbin 302 is dependentlycontrolled by a tension controller.

Accordingly, the system 390 allows for the formation of a thin filmcomposite hollow fiber membrane along a continuously moving hollowfiber, thus improving efficiency and creating long, continuousmembranes. In addition, unlike systems that configure nip-rollers toremove excess first solution, a system that uses the apparatus 200 canbe configured to remove excess first solution from a hollow fiber and toproduce thin film composite hollow fiber membranes, without pressing ordamaging the hollow fiber.

FIG. 4 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes. In some implementations, a method 400can include passing a hollow fiber through the apparatus 200. In someimplementations, at 402 a hollow fiber is immersed in a first solutionprior to passing the hollow fiber through the apparatus. The firstsolution can be an aqueous solution containing monomeric arylenepolyamine, for example, an aqueous solution of 1,3-phenylenediamine.Then, at 404, the hollow fiber can be passed through the first hollowpassage defined by a housing between an inlet formed on a first surfaceof the housing and an outlet formed on a second surface of the housingopposite the first surface.

At 406, the vacuum draws gas through the first hollow passage, over thehollow fiber, and through a second hollow passage defined by thehousing. Doing so removes at least a portion of the first solution (thatis, the excess first solution) from an outer surface of the hollowfiber. A rate at which the gas is drawn by the vacuum is determined by aquantity of the excess first solution on the outer surface of the hollowfiber. In some implementations, the gas is ambient air. In someimplementations, the gas is an inert gas, for example, nitrogen.

In some implementations, after passing the hollow fiber through theoutlet, the hollow fiber can be immersed in a second solution at 408.The first and second solution can be immiscible, and contact between thefirst solution on the hollow fiber and the second solution can cause apolymerization reaction at an interface of the first solution and thesecond solution. In some implementations, the first solution is anaqueous solution containing monomeric arylene polyamine, for example, anaqueous solution of 1,3-phenylenediamine. In some implementations, thesecond solution is a water immiscible solvent containing monomeric acylhalide, for example, trimesoyl chloride in n-hexane. In someimplementations, after immersing the hollow fiber in a second solution,the hollow fiber can be dried in an air-drying tower at 410.

FIG. 5A shows an example of a perspective view of a secondimplementation of an apparatus 500. An apparatus 500 can include housing501. The housing can comprise metal or plastic, for examplepolytetrafluoroethylene, polyethylene, polypropylene, or acrylic. Ahollow fiber that has been immersed in a first solution (for example,the first solution 102 of FIG. 1) is passed through the apparatus 500from an inlet to an outlet via a hollow passage within the apparatus500. As the hollow fiber passes through the apparatus 500, a gas isflowed past a surface of the hollow fiber through a hollow passageformed in the apparatus 500. The flowing gas removes at least a portionof first solution from the surface of the hollow fiber (that is, theexcess first solution) from the outer surface of the hollow fiber.Removal of the excess first solution improves the quality of themembrane that results from interfacial polymerization. For example,excess first solution on the hollow fiber causes defects in themembrane. Accordingly, removing the excess first solution improves thequality and subsequent performance of the membrane.

In some implementations, the housing 501 includes two plates, a firstplate 512 and a second plate 514. The first plate 512 can be a top plateand the second plate 514 can be a bottom plate. In some implementations,the first plate 512 can be the bottom plate and the second plate 514 canbe the top plate. In some implementations, the first plate 512 can be atop plate and the second plate 514 can be a bottom plate. The housing501 is formed by positioning and aligning the top and bottom plates. Insome implementations, the first plate 512 and the second plate 514 areseparably coupled by a coupling mechanism. This can be beneficial formaking adjustments to the hollow fiber or for threading the hollow fiberthrough the apparatus initially. The coupling mechanism can include ahinge 516, a magnet 518, multiple magnets 518, or a combination of twoor all of them (FIGS. 5A, 5C). Any coupling mechanism that allows thefirst and second plate to be reversibly opened and closed can besuitable, for example, a hinge and a clasp.

The first surface 503 of the first plate 512 can define at least aportion of the inlet 502, and the first surface 515 of the second plate512 can define the remainder of the inlet 502 (FIGS. 5A, 5D). The secondsurface 505 of the first plate 512 can define at least a portion of theoutlet 504, and the second surface 517 of the second plate 514 candefine the remainder of the outlet 504 (FIGS. 5A, 5D). A first hollowpassage 506 connects the inlet and the outlet (FIGS. 5C, 5D). The firstplate 512 can define a first portion of the first hollow passage 506 andthe second plate 514 can define a second portion of the first hollowpassage 506. Accordingly, in some implementations the hollow passage isformed when the first and second plates are joined together (FIG. 5D).The inlet 502, outlet 504, and first hollow passage 506 can besufficiently large to allow a hollow fiber to pass through the apparatus500 without coming into contact with the sides of the first hollowpassage 506. The inlet 502, outlet 504, and the first hollow passage 506can have any cross-sectional shape that can accommodate the hollowfiber. For example, the inlet, outlet, and first hollow passage can havea triangular, rectangular, star-shaped or substantially circularpassage. The inlet, outlet, and first hollow passage can have, forexample, a diameter of 0.5 to 10 mm. Alternatively, the inlet, outlet,and first hollow passage can have, for example, a diameter of 0.5 to 2.0mm. Further, the inlet, outlet, and first hollow passage can beconfigured to accommodate the desired hollow fiber. For example, highpressure applications require thin film composite hollow fiber membranesthat are thin enough to withstand operating pressures. A hollowmicrofiber with a diameter of 80 μm can be used for high-pressureapplications such as gas separation, reverse osmosis, or nanofiltration.Alternatively, low pressure applications such as microfiltration orultrafiltration require thicker thin film composite hollow fibermembranes in order to minimize pressure drop through the bore of thefiber. A hollow fiber with a diameter of 1.5 mm can be used forultrafiltration or microfiltration. Accordingly, the inlet, outlet, andfirst hollow passage can be configured to these or other hollow fiberdiameters. In some implementations, the diameter of the inlet, outlet,and first hollow passage can be between 150%-200% wider than thediameter of the hollow fiber.

FIG. 5B shows an example of a front view of an apparatus 500 with plate512 and 514. Both the first plate 512 and the second plate 514 can havea substantially rectangular cross-section. The substantially rectangularcross-section allows the hollow fiber to pass through the apparatus 500.In some implementations, the first plate 512 can define at least aportion of the inlet 502 and the outlet 504, and the second plate 514can define a remainder of the inlet 502 and the outlet 504 (FIGS. 5B,5D). The first plate 512 and second plate 514 can define a first hollowpassage 506 as described previously.

FIG. 5C shows an example of a cross-sectional top view of an apparatus500. The first hollow passage 506 can be configured to allow a hollowfiber to pass through the apparatus 500 in a direction from the inlet tothe outlet as described previously. The apparatus 500 can include afirst compressed gas port 508 and a second compressed gas port 510formed on the housing 501. In some implementations, the first and secondcompressed gas ports are formed on the second plate 514. In someimplementations, the first and second compressed gas ports are formed onthe second surface 515 adjacent to the outlet 504. The first and secondgas ports are configured to be connected to one or more compressed gassources.

The housing 501 can define a second hollow passage 510 between the firstcompressed gas port 508 and the first hollow passage 506. The housing501 can define a third hollow passage 511 between the second compressedgas port 509 and the first hollow passage 506. In some implementations,the second plate 514 can define the first and second compressed gasports and the second and third hollow passages. In some implementations,the second hollow passage 510 and the third hollow passage 511 share acommon outlet to the first hollow passage. The common outlet can bepositioned substantially at a mid-point of the first hollow passage 506.

The first and second compressed gas ports 508 and 509 can be configuredto flow compressed gas through the second and third hollow passages 510and 511 in a direction toward the inlet 502, in a direction that is atleast partially opposite to the movement of the hollow fiber through theapparatus 500. The angle of the second and third hollow passages,relative to the first hollow passage, can be configured in order thatthe movement of compressed air through the second and third hollowpassages removes at least a portion of the first solution (that is, theexcess first solution) from an outer surface of the hollow fiber. Thesecond and third hollow passages 510 and 511 are positionedsymmetrically on substantially opposite sides of the first hollowpassage 506.

The rate at which the compressed gas flows over the hollow fiber isdetermined by a quantity of the excess first solution on the outersurface of the hollow fiber. The flow rate of the compressed gas can beoptimized, for example by optimizing for the diameter of the firsthollow passage, the length of the first hollow passage, or the diameterof the hollow fiber. In some implementations, the flow rate of thecompressed gas is controlled by a pressure regulator, a needle valve, amass flow meter, or a combination of a pressure regulator and needlevalve or mass flow meter. In some implementations, the compressed gas iscompressed ambient air. In some implementations, the compressed gas isan inert gas, for example, nitrogen. Removing the excess first solutionimproves the quality of the membrane that results from interfacialpolymerization. For example, excess first solution on the hollow fibercauses defects in the membrane. Accordingly, removing the excess firstsolution improves the quality and subsequent performance of themembrane.

In an alternative embodiment, the inlet 502, outlet 504, first hollowpassage 506, first compressed gas port 508, second compressed gas port509, second hollow passage 510 and third hollow passage 511 can bedefined by the first plate 512. In another alternative embodiment, theinlet 502, outlet 504, first hollow passage 506, first compressed gasport 508, second compressed gas port 509, second hollow passage 510, andthird hollow passage 511 can be defined by the second plate 514. Thesecond hollow passage 510 and third hollow passage 511 are configuredfor the movement of air or gas through the second and third hollowpassages. The hollow fiber 550 does not pass through the second hollowpassage 510 or the third hollow passage 511.

In some implementations, the device 500 contains additional compressedgas ports and additional hollow passages. The additional compressed gasports and additional hollow passages can be positioned as pairs,symmetrically on substantially opposite sides of the first hollowpassage 506.

FIG. 6 shows an example of a system 690 configured to produce thin filmcomposite hollow fiber membranes using an apparatus. In someimplementations, the apparatus 500 can be part of a system 690 forproducing a thin film composite on the outer surface of a hollow fiber.The system can include a hollow fiber 650 that can travel between twobobbins 602 and 604 over a series of rollers 603. The hollow fiber 650can be a semi-permeable hollow fiber. The hollow fiber can be woundaround the first bobbin 602 to create a spool of hollow fiber. Thehollow fiber 650 can then unspool from the first bobbin 602 and travelthe series of rollers 603. The rollers are positioned to direct thehollow fiber 650 into a first solution 606, in order to saturate or coatthe hollow fiber 650 with the first solution 606. The first solution 606can be held in a first reservoir 607. The first solution can be anaqueous solution containing monomeric arylene polyamine, for example, anaqueous solution of 1,3-phenylenediamine. The hollow fiber then passesthrough the apparatus 500. A compressed gas source 610 is connected tothe apparatus 500 via the compressed gas ports. In some implementations,more than one compressed gas source is connected to the apparatus 500via the first and second compressed gas ports. For example, a firstcompressed gas source can be connected to the first compressed gas port508 and a second compressed gas source can be connected to the secondcompressed gas port 509. Alternative, a first compressed gas source canbe connected to both the first compressed gas port 508 and the secondcompressed gas port 509. The apparatus 500 and the compressed gas sourceor sources 610 remove the excess first solution from the hollow fiber650. The hollow fiber can then be immersed in a second solution 608. Thesecond solution can be held in a second reservoir 609. The secondsolution can be a water immiscible solvent containing monomeric acylhalide, for example, a solution of trimesoyl chloride in n-hexane. Afterimmersing in the second solution, the hollow fiber includes a thin filmcomposite on the outer surface of the membrane, forming a thin filmcomposite hollow fiber membrane 651. The thin film composite hollowfiber membrane 651 then passes through an air drying tower 612. The airdrying tower 612 is configured to evaporate unreacted second solutionand thermally cure the formed composite membrane. The air drying tower612 can include a heat gun or a dryer. The heat supplied by the airdrying tower 612 can reach temperatures of 150° C. to dry and cure thethin film composite hollow fiber membrane. The thin film compositehollow fiber membrane 651 can then travel to a second bobbin 604configured to receive the thin film composite hollow fiber membrane 651.The thin film composite hollow fiber membrane 651 can be wound aroundthe second bobbin 604.

The system can include a motor to drive the movement of the hollowfiber, for example, by driving the rotation of the bobbins, the rollers,or a combination of the bobbins and rollers. In some implementations,the second bobbin 604 is connected to a motor and set to a speed thatallows for removal of the excess first solution 606 as well as drying ofthe thin film composite hollow fiber membrane 651. In someimplementations, the rotation of bobbin 602 is dependently controlled bya tension controller. Accordingly, the system 690 allows for theformation of a thin film membrane along a continuously moving hollowfiber, thus improving efficiency and creating long, continuousmembranes. In addition, unlike systems that configure nip-rollers toremove excess first solution, a system that uses the apparatus 500 canbe configured to remove excess first solution from a hollow fiber and toproduce thin film composite hollow fiber membranes, without pressing ordamaging the hollow fiber.

FIG. 7 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes using a second implementation of anapparatus. In some implementations, a method 700 includes immersing ahollow fiber in a first solution at 702. The first solution can be anaqueous solution containing monomeric arylene polyamine, for example, anaqueous solution of 1,3-phenylenediamine. At 704, a hollow fiber ispassed through a first hollow passage defined by a housing between aninlet formed on a first surface of the housing and an outlet formed on asecond surface of the housing opposite the first surface.

At 706, a compressed gas source flows a compressed gas through the gasports, through a second hollow passage and a third hollow passagedefined by the housing, and through the first hollow passage. In thefirst hollow passage the compressed gas flows over the hollow fiber. Thecompressed gas can be flowed toward the inlet in a direction at leastpartially opposite a direction that the hollow fiber passes through theapparatus. Doing so removes at least a portion of the first solution(that is, the excess first solution) from an outer surface of the hollowfiber. A rate at which the gas flows over the hollow fiber is determinedby a quantity of the excess first solution on the outer surface of thehollow fiber. In some implementations, the gas is compressed ambient airor a compressed inert gas, such as nitrogen.

In some implementations, after passing the hollow fiber through theoutlet, the method can include immersing the hollow fiber in a secondsolution at 708. The first and second solution can be immiscible, andcontact between the first solution on the hollow fiber and the secondsolution can cause a polymerization reaction at an interface of thefirst solution and the second solution. In some implementations, thefirst solution is an aqueous solution containing monomeric arylenepolyamine, for example, an aqueous solution of 1,3-phenylenediamine. Insome implementations, the second solution is a water immiscible solventcontaining monomeric acyl halide, for example, trimesoyl chloride inn-hexane.

In some implementations, at 710 the hollow fiber can be dried in an airdrying tower. The air drying tower 612 is configured to evaporateunreacted second solution and thermally cure the formed compositemembrane. The air drying tower 612 can include a heat gun or a dryer.The heat supplied by the air drying tower 612 can reach temperatures of150° C. to dry and cure the thin film composite hollow fiber membrane.

FIG. 8A shows an example of a third implementation of an apparatus 800.

In some implementations, an apparatus 800 can include a first tubularmember 812 and a second tubular member 814. The second tubular member814 can be positioned coaxially within the first tubular member 812. Insome implementations, a longitudinal axis of the first tubular member836 and a longitudinal axis of the second tubular member 838 aresubstantially perpendicular to each other.

The first and second tubular members can comprise metal or plastic, forexample, polytetrafluoroethylene, polyethylene, polypropylene, oracrylic. The inner surface of the second tubular member 814 defines afirst hollow passage 806. A hollow fiber that has been immersed in afirst solution (for example, the first solution 102 of FIG. 1) is passedthrough the apparatus 800 from an inlet 802 toward an outlet 804 via thefirst hollow passage 806.

The first tubular member and second tubular member define an annularregion 813 between an inner surface of the first tubular member and anouter surface of the circumferential wall of the second tubular member.The annular region can be sealed except for a gas inlet port 808 andapertures 803, as discussed below. The first tubular member can befluidly coupled to a compressed gas inlet port 808. In someimplementations, a third tubular member 811 is attached to the firsttubular member, wherein a first end of the third tubular member 811 isfluidly coupled to a circumferential surface of the first tubular member812, and the compressed gas inlet port 808 is formed on a second end ofthe third tubular member 811. In some implementations, the third tubularmember is attached to the first tubular member at a point substantiallymidway between ends of the first tubular member. The compressed gasinlet port 808 is configured to be coupled to a compressed gas source.Accordingly, compressed gas can flow from the compressed gas port 808,through the third tubular member 811, and into the annular space 813.

FIG. 8B shows an example of a top view of the apparatus 800. Asdiscussed previously, the first tubular member 812 and the secondtubular member 814 can enclose an annular region 813. The second tubularmember 814 can define a first hollow space 806. The hollow space 806 canbe configured to allow a hollow fiber 850 to pass through the apparatus800 (FIG. 8A). The inlet 802, outlet 804, and first hollow passage 806can be sufficiently large to allow a hollow fiber to pass through theapparatus 800 without coming into contact with the sides of the firsthollow passage 806. The inlet 802, outlet 804, and first hollow passage806 can have any cross-sectional shape that can accommodate the hollowfiber. For example, the inlet, outlet, and first hollow passage can havea triangular, rectangular, star-shaped or substantially circularpassage. The inlet, outlet, and first hollow passage can have, forexample, a diameter of 0.5 to 10 mm. Alternatively, the inlet, outlet,and first hollow passage can have, for example, a diameter of 0.5 to 2.0mm. Further, the inlet, outlet, and first hollow passage can beconfigured to accommodate the desired hollow fiber. For example, highpressure applications require thin film composite hollow fiber membranesthat are thin enough to withstand operating pressures. A hollowmicrofiber with a diameter of 80 μm can be used for high-pressureapplications such as gas separation, reverse osmosis, or nanofiltration.Alternatively, low pressure applications such as microfiltration orultrafiltration require thicker thin film composite hollow fibermembranes in order to minimize pressure drop through the bore of thefiber. A hollow fiber with a diameter of 1.5 mm can be used forultrafiltration or microfiltration. Accordingly, the inlet, outlet, andfirst hollow passage can be configured to these or other hollow fiberdiameters. In some implementations, the diameter of the inlet, outlet,and first hollow passage can be between 150%-200% wider than thediameter of the hollow fiber.

FIG. 8C shows an example of a cross-sectional side view of an apparatus800. The second tubular member 814 can include a circumferential wallthat has multiple apertures 803, which are through-holes in thecircumferential wall of the second tubular member 814. The apertures canbe distributed at multiple positions around the circumference of thesecond tubular member and at multiple positions along the x-axis (FIG.8C). This allows the compressed air that is flowed into the annularspace to be flowed at multiple angles and locations relative to thesurface of the hollow fiber. In some implementations, the aperturessubstantially surround the hollow fiber as it passes through theapparatus 800.

A compressed gas source connected to the compressed gas port 808 canflow compressed air through the third tubular member 811, into theannular space 813, and through the multiple aperture 803 into the firsthollow passage 806. In some implementations, the compressed gas iscompressed ambient air. In some implementations, the compressed gas isan inert gas, for example, nitrogen.

The apertures 803 can be configured such that the compressed gas canflow through the first hollow passage 806 in a direction that is atleast partially opposite to the movement of the hollow fiber 850 throughthe apparatus 800. Each aperture 803 can have an axis 830 that forms anangle 831, relative to an axis of the second tubular member 832.Accordingly, the angle 831 is configured to flow the compressed gas overthe hollow fiber 850 in a direction at least partially opposite to adirection in which the hollow fiber is passed through the hollow portion806 of the second tubular member 814. In some implementations, the angle831 is greater than zero degrees and less than ninety degrees. In someimplementations, the angle is substantially 45 degrees. In someimplementations, the angles 831 for the multiple apertures are equal toeach other. In some implementations, the angles 831 for the multipleapertures are different from each other.

Flowing gas through the apertures 803 removes at least a portion of thefirst solution (that is, the excess first solution) from an outersurface of the hollow fiber. The rate at which the compressed gas flowsover the hollow fiber is determined by a quantity of the excess firstsolution on the outer surface of the hollow fiber. Removing the excessfirst solution improves the quality of the membrane that results frominterfacial polymerization. For example, excess first solution on thehollow fiber causes defects in the membrane. Accordingly, removing theexcess first solution improves the quality and subsequent performance ofthe membrane. The flow rate of the compressed gas can be optimized, forexample by optimizing for the diameter of the first hollow passage, thelength of the first hollow passage, or the diameter of the hollow fiber.In some implementations, the flow rate of the compressed gas iscontrolled by a pressure regulator, a needle valve, a mass flow meter,or a combination of a pressure regulator and needle valve or mass flowmeter.

FIG. 9 shows an example of a system 990 configured to produce thin filmcomposite hollow fiber membranes using an apparatus. In someimplementations, the apparatus 800 can be part of a system 990 forproducing a thin film composite on the outer surface of a hollow fibermembrane. The system can include a hollow fiber 950 that can travelbetween two bobbins 902 and 904 over a series of rollers 903. Therollers are positioned to direct the hollow fiber 950 into a firstsolution 906, in order to saturate or coat the hollow fiber 950 with thefirst solution 906. The first solution 906 can be held in a firstreservoir 907. The first solution can be an aqueous solution containingmonomeric arylene polyamine, for example, an aqueous solution of1,3-phenylenediamine. The hollow fiber then passes through the apparatus800. A compressed gas source 910 is connected to the apparatus 800 viathe compressed gas port 808. The apparatus 800 and the compressed gassource 910 remove the excess first solution from the hollow fiber 950.The hollow fiber can then be immersed in a second solution 808. Thesecond solution can be held in a second reservoir 809. The secondsolution can be a water immiscible solvent containing monomeric acylhalide, for example, a solution of trimesoyl chloride in n-hexane. Afterimmersing in the second solution, the hollow fiber includes a thin filmcomposite on the outer surface of the membrane, forming a thin filmcomposite hollow fiber membrane 951. The thin film composite hollowfiber membrane 951 then passes through an air drying tower 912. The airdrying tower 912 is configured to evaporate unreacted second solutionand to thermally cure the formed composite membrane. The air dryingtower 912 can include a heat gun or a dryer. The heat supplied by theair drying tower 912 can reach temperatures of 150° C. to dry and curethe thin film composite hollow fiber membrane. The thin film compositehollow fiber membrane 951 can then travel to a second bobbin 904configured to receive the thin film composite hollow fiber membrane 951.The thin film composite hollow fiber membrane 951 can be wound aroundthe second bobbin 904. In some implementations, the second bobbin 904 isconnected to a controlled-speed motor and set to a speed that allows forremoval of the excess first solution 906 as well as drying of the thinfilm composite hollow fiber membrane 951. In some implementations, therotation of bobbin 902 is dependently controlled by a tensioncontroller.

The system can include a motor to drive the movement of the hollowfiber, for example, by driving the rotation of the bobbins, the rollers,or a combination of the bobbins and rollers. Accordingly, the system 990allows for the formation of a thin film membrane along a continuouslymoving hollow fiber, thus improving efficiency and creating long,continuous membranes. In addition, unlike systems that configurenip-rollers to remove excess first solution, a system that uses theapparatus 800 can be configured to remove excess first solution from ahollow fiber and to produce thin film composite hollow fiber membranes,without pressing or damaging the hollow fiber.

All three of the systems (390, 690, and 990) can use any of theapparatus 200, 500, and 800 interchangeably. In addition, all threesystems can utilize more than one type or more than once instance of anyof the three apparatuses 200, 500, and 800. A system can includemultiple apparatuses in series, for example a system configured so thatafter the hollow fiber is immersed in the first solution, the hollowfiber passes through a first apparatus and into a second apparatus. Thefirst and second apparatus can be the same apparatus or differentapparatuses from the group including apparatuses 200, 500, and 800. Thenumber of apparatus that can be utilized in series is not limited to oneor two. Accordingly, many combinations of apparatuses are possible.

FIG. 10 is a flowchart showing an example method of producing thin filmcomposite hollow fiber membranes. In some implementations, a method 1000includes immersing a hollow fiber in a first solution at 1002. The firstsolution can be an aqueous solution containing monomeric arylenepolyamine, for example, an aqueous solution of 1,3-phenylenediamine. At1004, a first tubular member is positioned around a second tubularmember to define an annular region. At 1006, a hollow fiber is passedthrough a hollow portion of the second tubular member from a first endof the second tubular member toward a second end of the second tubularmember.

At 1008, compressed gas is flowed into the annular region and into thehollow portion through multiple apertures formed on a circumferentialwall of the second tubular member in a direction at least partiallyopposite to the direction in which the hollow fiber is passed throughthe second tubular member. Flowing the compressed gas over the hollowfiber removes at least a portion of the first solution (that is, theexcess first solution) from an outer surface of the hollow fiber. A rateat which the gas flows over the hollow fiber is determined by a quantityof the excess first solution on the outer surface of the hollow fiber.In some implementations, the gas is compressed ambient air or acompressed inert gas, such as nitrogen.

In some implementations, after passing the hollow fiber through thesecond tubular member, the hollow fiber is immersed in a second solutionat 1010. The first and second solution can be immiscible, and contactbetween the first solution on the hollow fiber and the second solutioncauses a polymerization reaction at an interface of the first solutionand the second solution. In some implementations, the first solution isan aqueous solution containing monomeric arylene polyamine, for example,an aqueous solution of 1,3-phenylenediamine. In some implementations,the second solution is a water immiscible solution containing monomericacyl halide, for example, a solution of trimesoyl chloride in n-hexane.

In some implementations, at 1012, after immersing the hollow fiber in asecond solution, the hollow fiber is dried in an air drying tower. Theair drying tower 1012 is configured to evaporate unreacted secondsolution and thermally cure the formed composite membrane. The airdrying tower 1012 can include a heat gun or a dryer. The heat suppliedby the air drying tower 1012 can reach temperatures of 150° C. to dryand cure the thin film composite hollow fiber membrane.

Examples Preparation of a thin film membrane using an apparatus 500 Amesoporous hollow fiber with 20-100 nm pores and a surface porosity of8-20% was partially immersed into a first solution of 0.5-2.5 wt % m-PDAfor 10 minutes to saturate the hollow fiber with the first solution.Excess first solution was removed from the hollow fiber using anapparatus 500. The droplet-free porous hollow fiber was next immersed ina second solution of 0.05-0.2 wt/vol % trimesoyl chloride in n-hexane togenerate the thin film composite membrane on the outer surface of thehollow fiber. The hollow fiber with thin film composite membrane wasthen dried in an air drying tower and collected on a bobbin. Gaspermeation results indicate that the prepared membrane has selectivityfor helium over other gases, for example, CO₂ (Table 1). Each of threeexperiments was a pure gas permeation test with a feed pressure of 100psi over a membrane area of 65.4 cm².

TABLE 1 Gas Permeance Experiment Permeance (Gas Permeance Unit)Selectivity number He N₂ CH₄ CO₂ He/N₂ He/CH₄ He/CO₂ 1 15.26 0.02 0.010.40 837.8 1148.1 38.3 2 15.36 0.01 0.01 0.43 1200.0 1733.3 35.5 3 14.960.02 0.01 0.40 980.6 2338.5 37.5

A number of implementations of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the disclosure.

What is claimed is:
 1. An apparatus comprising: a housing; an inletformed on a first surface of the housing; an outlet formed on a secondsurface of the housing opposite the first surface, the housing defininga first hollow passage between the inlet and the outlet, the firsthollow passage configured to allow a hollow fiber to pass through thehousing; and a vacuum port formed on a third surface of the housing, thehousing defining a second hollow passage between the first hollowpassage and the vacuum port, the vacuum port configured to draw gas fromthe inlet and the outlet and through the first hollow passage and thesecond hollow passage.
 2. The apparatus of claim 1, wherein the thirdsurface is substantially perpendicular to the first surface or thesecond surface.
 3. The apparatus of claim 2, wherein the second hollowpassage is substantially perpendicular to the first hollow passage. 4.The apparatus of claim 1, wherein the housing comprises a first plateand a second plate configured to be joined together to form the housing.5. The apparatus of claim 4, wherein the first plate defines at least aportion of the first hollow passage and the second plate defines aremainder of the first hollow passage.
 6. The apparatus of claim 4,wherein the second plate defines the second hollow passage.
 7. Theapparatus of claim 4, wherein the first plate and the second plate areseparably coupled by a coupling mechanism.
 8. The apparatus of claim 7,wherein the coupling mechanism comprises a hinge or a magnet or a hingeand a magnet.
 9. The apparatus of claim 4, wherein the first plate has asubstantially rectangular cross-section and the second plate has asubstantially T-shaped cross-section.
 10. A system comprising: anapparatus comprising: a housing, an inlet formed on a first surface ofthe housing, an outlet formed on a second surface of the housingopposite the first surface, the housing defining a first hollow passagebetween the inlet and the outlet, the first hollow passage configured toallow a hollow fiber to pass through the housing, and a vacuum portformed on a third surface of the housing, the housing defining a secondhollow passage between the first hollow passage and the vacuum port, thevacuum port configured to draw gas from the inlet and the outlet andthrough the first hollow passage and the second hollow passage; a vacuumsource coupled to the vacuum port, the vacuum source configured to applyvacuum to the vacuum port to draw the gas from the inlet and the outletand through the first hollow passage and the second hollow passage. 11.The system of claim 10, wherein the housing comprises a first plate anda second plate configured to be joined together to form the housing. 12.The system of claim 11, wherein the first plate defines at least aportion of the first hollow passage and the second plate defines aremainder of the first hollow passage.
 13. The system of claim 11,wherein the second plate defines the second hollow passage.
 14. Thesystem of claim 11, wherein the first plate and the second plate areseparably coupled by a coupling mechanism.
 15. The system of claim 14,wherein the coupling mechanism comprises a hinge or a magnet or a hingeand a magnet.
 16. A method comprising: passing a hollow fiber through afirst hollow passage defined by a housing between an inlet formed on afirst surface of the housing and an outlet formed on a second surface ofthe housing opposite the first surface, wherein the hollow fiber isimmersed in a first solution prior to passing the hollow fiber throughthe first hollow passage; and while passing the hollow fiber through thefirst hollow passage, drawing, by vacuum, a gas through the first hollowpassage and over the hollow fiber through a second hollow passagedefined by the housing, the second hollow passage terminating in avacuum port formed on a third surface of the housing, wherein drawingthe gas over the hollow fiber removes at least a portion of the firstsolution from an outer surface of the hollow fiber.
 17. The method ofclaim 16, further comprising, after passing the hollow fiber through theoutlet, immersing the hollow fiber in a second solution, wherein thefirst solution and the second solution are immiscible, wherein contactbetween the first solution and the second solution causes apolymerization reaction at an interface of the first solution and thesecond solution.
 18. The method of claim 17, wherein immersing thehollow fiber in a first solution comprises immersing the hollow fiber inan aqueous solution comprising monomeric arylene polyamine.
 19. Themethod of claim 18, wherein immersing the hollow fiber in a secondsolution comprises immersing the hollow fiber in a solution comprising amonomeric acyl halide.
 20. The method of claim 16, wherein drawing, byvacuum, the gas through the first hollow passage and over the hollowfiber through the second hollow passage comprises drawing the gasthrough the inlet and the outlet towards the vacuum port.